How does sirimiri arise?

2003/01/21 Carton Virto, Eider - Elhuyar Zientzia

• Fisika
• Klima

The theory has been published by New York scientists. They have not taken as an example the sirimiri of Euskal Herria, but it does not matter, it will serve ours and the explanation.

Ten times smaller than raindrops

Normal raindrops have a couple of millimeters and fall at 9 meters per second. Sirimiri drops measure one-fifth of the millimeter and fall in the clouds at half a meter per second. They seem to float in the air, but we know they wet as much or more as others.

According to the theory accepted by experts, raindrops occur in two phases. In the nucleation phase they reach a minimum growth size in the form of drops, of about 0.04 millimeters. When they have this size, they begin to fall through the cloud and, under the influence of strong wind currents, collide, unite and increase. They reach a minimum size of 20 minutes and reach the size of sirimiri drops in an hour.

However, in the clouds emitting the sirimiri the process occurs in a quarter of an hour, in much warmer clouds. How to demonize?

Meteorologists believe that in the quieter air whirlpools the drops condense and join faster, but they do not know to what extent this effect is so great. They do not know if it is enough to explain the sirimiri.

New York scientists have not clarified this, but have proposed a theory. According to them, the drops of sirimiri are also formed in two phases, that is, first the nucleation occurs and then one that follows the same pattern of the nucleation. After this second phase, scientists have seen the drops come together and grow very quickly. Drops of sirimiri, therefore, should at first exceed two size limits, but then grow very quickly.

More information about the research on the website of the journal Nature.